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Extra virgin olive oil (EVOO) is one of the main ingredients of the Mediterranean diet. It is claimed as a functional food for its unique content of health-promoting compounds. Tyrosol (Tyr), Hydroxytyrosol (Htyr), and their phenolic derivatives present in EVOO show beneficial properties, and their identification and quantification, both in their free form and after the hydrolysis of more complex precursors, are important to certify its quality. An alternative method for quantifying free and total Tyr and Htyr in EVOO is presented using an LC–MS interface based on electron ionization (EI), called liquid electron ionization (LEI). This method requires neither sample preparation nor chromatography; the sample is diluted and injected. The selectivity and sensitivity were assessed in multiple reaction monitoring mode (MRM), obtaining confirmation and quantification in actual samples ranging from 5 to 11 mg/Kg for the free forms and from 32 to 80 mg/Kg for their total amount after hydrolysis. Two MS/MS transitions were acquired for both compounds using the Q/q ratios as confirmatory parameters. Standard addition calibration curves demonstrated optimal linearity and negligible matrix effects, allowing a correct quantification even without expensive and difficult to find labeled internal standards. After several weeks of operation, the system’s repeatability was excellent, with an intraday RSD (%) spanning from five to nine and an interday RSD (%) spanning from 9 to 11.

This review article traces the history of the use of liquid chromatography coupled with mass spectrometry (LC-MS) using electron ionization (EI) from the first attempts up to the present day. At the time of the first efforts to couple LC to MS, 70 eV EI was the most common ionization technique, typically used in gas chromatography-mass spectrometry (GC-MS) and providing highly reproducible mass spectra that could be collated in libraries. Therefore, it was obvious to transport this dominant approach to the early LC-MS coupling attempts. The use of LC coupled to EI-MS is challenging mainly due to restrictions related to high-vacuum and high-temperature conditions required for the operation of EI and the need to remove the eluent carrying the analyte before entering the ion source. The authors will take readers through a journey of about 50 years, showing how through the succession of different attempts it has been possible to successfully couple LC with EI-MS, which in principle appear to be incompatible.

Mass spectrometry has been the “gold standard” for drugs of abuse (DoA) analysis for many decades because of the selectivity and sensitivity it affords. Recent progress in all aspects of mass spectrometry has seen significant developments in the field of DoA analysis. Mass spectrometry is particularly well suited to address the rapidly proliferating number of very high potency, novel psychoactive substances that are causing an alarming number of fatalities worldwide. This review surveys advancements in the areas of sample preparation, gas and liquid chromatography‐mass spectrometry, as well as the rapidly emerging field of ambient ionization mass spectrometry. We have predominantly targeted literature progress over the past ten years and present our outlook for the future.

MACCHINA PER ANALISI CHIMICA COMPRENDENTE LA COMBINAZIONE DELLA SPETTROMETRIA DI MASSA A IONIZZAZIONE ELETTRONICA CON LA CROMATOGRAFIA LIQUIDA

Current mass spectrometry-based methodologies for synthetic organic reaction monitoring largely use electrospray ionization (ESI), or other related atmospheric pressure ionizationbased approaches. Monitoring of complex, heterogeneous systems may be problematic because of sampling hardware limitations, and many relevant analytes (neutrals) exhibit poor ESI performance. An alternative monitoring strategy addressing this significant impasse is condensed phase membrane introduction mass spectrometry using liquid electron ionization (CP-MIMS-LEI). In CP-MIMS, a semipermeable silicone membrane selects hydrophobic neutral analytes, rejecting particulates and charged chemical components. Analytes partition through the membrane, and are then transported to the LEI interface for sequential nebulization, vaporization, and ionization. CP-MIMS and LEI are both ideal for continuous monitoring applications of hydrophobic neutral molecules. We demonstrate quantitative reaction monitoring of harsh, complex reaction mixtures (alkaline, acidic, heterogeneous) in protic and aprotic organic solvents. Also presented are solvent-membrane compatibility investigations and, in situ quantitative monitoring of catalytic oxidation and alkylation reactions.

Liquid Electron Ionization (LEI), is an innovative liquid chromatography-mass spectrometry (LC–MS)interface that converts liquid HPLC eluent to the gas-phase in a mass spectrometer equipped with anelectron ionization (EI) source. LEI extends the electronic spectra libraries access to liquid chromatog-raphy, providing a powerful tool in the untargeted approacssh. Negligible matrix effects allow accuratequantitative information. The purpose of this research was to evaluate the main aspects concerning theinterfacing process. These fundamental studies were necessary to understand the mechanism of LEI indetails, and improve the interfacing process, especially regarding robustness and sensitivity. Hardwarecomponents were installed to prevent analytes precipitation, reduce thermal decomposition of sensitivecompounds, and to stabilize the nano-flow delivery with different mobile-phase compositions. Partic-ular attention was devoted to insulating the heated vaporization area from the LC part of the system.Experiments were performed to optimize the interface inner capillary dimensions, and other operativeparameters, including temperature, gas and liquid flow rates. Test compounds of environmental interestwere selected based on molecular weight, thermal stability, volatility, and polarity. Robustness was eval-uated with a set of replicated injections and calibration experiments using a soil matrix as a test sample.MRM detection limits in the low-picogram range were obtained for five pesticides belonging to differentclasses in a soil sample. High-quality electron ionization mass spectra of a mixture of pesticides werealso obtained.

Buprenorphine and its metabolites are routinely monitored to assess patient compliance with drug detoxification programs or as pain killers. A rapid method for the simultaneous analysis of buprenorphine, norbuprenorphine, and glucuronides in urine using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed. Urine samples were diluted in water containing formic acid 0.1% and directly injected into the UHPLC-MS/MS system without any sample pretreatment. Quality control (QC) samples, prepared using 20 different urine matrices, fortified at 3 concentration levels, were quantified using four deuterated internal standards. The accuracy values obtained spanned from 90 to 114% with repeatability lower than 10% also in the inter-day between batch experiments. Matrix effects (ME), evaluated before correction with internal standards using Matuszewski procedure, mainly affected the analysis of buprenorphine glucuronide. The use of deuterated internal standards (IS) for each analyte was necessary to compensate for ME and was essential in the determination of glucuronides. The method was applied to 30 real urine samples from patients under a detoxification therapy. Duplicate analyses were performed with the presented method and compared with another method which involves a standard hydrolysis procedure. Real sample results were compared showing a good performance agreement, with differences between the two methods lower than ±20% in the quantification results.

Electron ionization (EI) is a unique and advantageous ionization technique typically employed in gas chromatography-mass spectrometry (GC-MS). Here are presented two different approaches to benefit from EI in liquid chromatography-mass spectrometry (LC-MS). The first EI-based interface exploits EI of vibrationally cold molecules in supersonic molecular beams (SMBs) (hence named Cold EI). This system and its operational methods are centred on pneumatic spray formation of the liquid flow in a heated vaporization chamber, full thermal vaporization of the sample compounds and their subsequent EI as vibrationally cold molecules in the SMB after their supersonic expansion from a supersonic nozzle. Cold EI mass spectrum exhibits the standard EI fragments with enhanced molecular ion. The second EI-based interface is called Liquid-EI (LEI), and it is based on the nebulization of the liquid phase carrying the analytes inside a specifically designed region where the vaporization of solutes occurs at atmospheric pressure before entering the high-vacuum ion source. LEI guarantees more flexibility towards low volatile and thermolabile molecules analysis in respect to previous versions of this approach. The fine control of the vaporization temperature and the inertness of the new vaporization surface can enhance the overall interface performances. LEI generates typical EI mass spectra for the undoubted identification of targeted and nontargeted analytes. The two systems feature broad linear dynamic range, uniform response both for polar and nonpolar compounds and lack of matrix ion suppression effects that plague electrospray ionization and atmospheric pressure chemical ionization. These features are shown, described and demonstrated in different examples and applications.

The role of diethylene glycol (DEG) as a co-solvent for selected organic and inorganic pollutants adsorbed onto the particulate matter in produced formation water (PFW) from offshore gas platforms is thoroughly evaluated. Artificial seawater samples were spiked with certified sediments containing several polycyclic aromatic hydrocarbons (PAH) and metals. Aliquots (1 L) containing no DEG and DEG at 3500 and 5000 mg L1 were kept in static and dynamic modes for 24 h before analysis to allow sufficient partitioning time between solid and liquid phases for the selected analytes. The Italian legislation on this matter sets 3500 mg L1 as the highest concentration for DEG in PFW. In our experiments, concentrations equal to and above the set limit were chosen to enhance any possible co-solvent effect. Real PFWsamples were also analysed, both with and without DEG. The analyses were conducted by using GC-MS for the PAH, and ICP-MS for the metals. A minor co-solvent effect was observed for low-molecular-weight PAH in the artificial seawater in static mode. Among metals, only iron showed an increase in solubility in the presence of DEG, demonstrating the co-solvent effect of DEG. The experiments in dynamic mode revealed no increase in the solubility of any other analytes in the liquid phase compared with static mode.

Dispersive liquid-liquid microextraction with and without ultrasound assistance (DLLME, UA-DLLME) and microextraction with packed sorbent (MEPS) methods for the extraction and determination of eight different benzodiazepines (BDZ) (chlordiazepoxide, flurazepam, bromazepam, oxazepam, lorazepam, clobazam, clonazepam, and flunitrazepam) in three commercial non-alcoholic and light alcoholic beverages were optimized and compared. Benzodiazepines are frequently used for their extensive diffusion and strong numbing effect in drug-facilitated crimes (DFC). The tiny small amount of sample required for DLLME and MEPS extraction makes them very suitable for specimens collected at the crime scene of DFCs. Microextraction techniques are of increasing interest thanks to their accordance to green analytical chemistry (GAC) guidelines providing good recovery values. Ultrasound assistance (UA-DLLME) was used to investigate whether this type of energy can improve the recoveries of the analytes. Analyses of the extracts were performed with reverse-phase capillary high-performance liquid chromatography with UV detection (HPLC − UV), thanks to low environmental impact, robustness, diffusion, and affordability. Recovery percentages at three different concentrations in the three beverages were between 14.30% and 103.28% with intraday and interday RSD lower than ± 2.78%. The same samples were extracted using a MEPS protocol, and the results were compared with those obtained with DLLME. MEPS gave recoveries between 20.90% and 101.88% for all matrices showing a better performance than DLLME at higher concentrations, though lower recoveries were observed with diluted samples.

In questo lavoro viene presentato un nuovo strumento, chiamato Liquid-EI (LEI), capace di interfacciare efficacemente la cromatografia liquida (LC) con la spettrometria di massa a ionizzazione elettronica (MS). L’interfaccia LEI è completamente indipendente e può essere adattata ad ogni sistema GC-MS per una rapida conversione ad LC-MS. Il suo funzionamento verrà di seguito descritto.

In this article, a detailed overview of the current high-performance liquid chromatography/mass spectrometry (HPLC/MS) instrumentation, suitable for the determination of a large number of pesticides, is reported. Particular emphasis is given to the role of the mass spectrometric apparatus involved in each interfacing technique with several information regarding the ionization processes, analyzer principles, and system configurations. The article is an up-to-date picture of the current instrumentation available and the reader will find only brief references to some important historical approaches that are no longer in use.

A novel liquid chromatography-mass spectrometry (LC-MS) interfacing concept is presented and discussed. The new interface, called Liquid-EI (LEI), is based on electron ionization (EI) but, differently from any previous attempt, the vaporization of solutes and mobile phase takes place at atmospheric pressure into a specifically designed region, called “vaporization micro-channel”, before entering the high-vacuum ion source. The interface is completely independent from the rest of the instrumentation, and can be adapted to any gas chromatography-mass spectrometry (GC-MS) system, as an add-on for a rapid LC-MS conversion. Pressure drop and temperature gradient between LC and MS were considered to enhance the analyte response and reduce band broadening and/or solute carryovers. A fused silica liner, placed inside the vaporization micro-channel, acts as an inert vaporization surface speeding up the gas-phase conversion of large molecules while lessening possible memory effects. The liner is easily replaceable for a quick and extremely simple interface maintenance. Proof of concept and detailed description of the interface are here presented.

Detection of target and non-target substances and their characterization in complex samples is a challenging task. Here we demonstrate that coating the electron ionization (EI) ion source of an LC-MS system with a sol-gel ceramic film can drastically improve the detection of high-molecular weight and high-boiling analytes. A new ion source coated with a ceramic material was developed and tested with a mixture of polycyclic aromatic hydrocarbons (PAH) with an increasing number of rings. Comparison of the results obtained with those for an uncoated stainless steel (SS) ion source shows a dramatic improvement in the MS signals, with a nearly 40-fold increase of the signal-to-noise ratio. We also demonstrate the ability of the new system to produce excellent chromatographic profiles for hard-to-detect hormones.

Polycyclic aromatic hydrocarbons (PAHs) are USEPA regulated priority pollutants. Their low aqueous solubility requires very sensitive analytical methods for their detection, typically involving preconcentration steps. Presented is the first demonstrated 'proof of concept' use of condensed phase membrane introduction mass spectrometry (CP-MIMS) coupled with direct liquid electron ionization (DEI) for the direct, on-line measurement of PAHs in aqueous samples. DEI is very well suited for the ionization of PAHs and other nonpolar compounds, and is not significantly influenced by the co-elution of matrix components. Linear calibration data for low ppb levels of aqueous naphthalene, anthracene, and pyrene is demonstrated, with measured detection limits of 4 ppb. Analytical response times (t10%-90% signal rise) ranged from 2.8 min for naphthalene to 4.7 min for pyrene. Both intra- and interday reproducibility has been assessed (<3% and 5% RSD, respectively). Direct measurements of ppb level PAHs spiked in a variety of real, complex environmental sample matrices is examined, including natural waters, sea waters, and a hydrocarbon extraction production waste water sample. For these spiked, complex samples, direct PAH measurement by CP-MIMS-DEI yielded minimal signal suppression from sample matrix effects (81%-104%). We demonstrate the use of this analytical approach to directly monitor real-time changes in aqueous PAH concentrations with potential applications for continuous on-line monitoring strategies and binding/adsorption studies in heterogeneous samples.

Sudden infant death syndrome (SIDS) and sudden intrauterine unexpected death syndrome (SIUDS) are an unresolved teaser in the social-medical and health setting of modern medicine and are the result of multifactorial interactions. Recently, prenatal exposure to environmental contaminants has been associated with negative pregnancy outcomes, and verification of their presence in fetal and newborn tissues is of crucial importance. A gas chromatography-tandem mass spectrometry (MS/MS) method, using a triple quadrupole analyzer, is proposed to assess the presence of 20 organochlorine pesticides, two organophosphate pesticides, one carbamate (boscalid), and a phenol (bisphenol A) in human brain tissues. Samples were collected during autopsies of infants and fetuses that died suddenly without any evident cause. The method involves a liquid-solid extraction using n-hexane as the extraction solvent. The extracts were purified with Florisil cartridges prior to the final determination. Recovery experiments using lamb brain spiked at three different concentrations in the range of 1-50 ng g-1 were performed, with recoveries ranging from 79 to 106 %. Intraday and interday repeatability were evaluated, and relative standard deviations lower than 10 % and 18 %, respectively, were obtained. The selectivity and sensitivity achieved in multiple reaction monitoring mode allowed us to achieve quantification and confirmation in a real matrix at levels as low as 0.2-0.6 ng g-1. Two MS/MS transitions were acquired for each analyte, using the Q/q ratio as the confirmatory parameter. This method was applied to the analysis of 14 cerebral cortex samples (ten SIUDS and four SIDS cases), and confirmed the presence of several selected compounds.

Benzodiazepines (BDZs) are widely used as tranquilizers and antidepressive drugs in common clinical practice. However, their ready availability and their synergistic effects with alcohol make them attractive for criminal intentions. To prove criminal action for legal reasons, it is often necessary to analyze beverage residues from a crime scene. Milk-based alcoholic drinks (whiskey creams) are gaining popularity due to their lower alcohol content pleasant taste. However, the complexity of this sample, containing proteins and fatty acids, can mask the presence of drugs or other substances in standard analysis methods. These characteristics make whiskey creams highly suitable for illicit purposes. In this study, eight BDZs, including diazepam, chlordiazepoxide, clobazam, flunitrazepam, bromazepam, flurazepam, nitrazepam and clonazepam, were extracted from whiskey cream using the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method and analyzed using GC-MS. The QuEChERS protocol can efficiently separate most of the matrix from the target compounds while maintaining acceptable recoveries. The presented method is simple and rapid and has been validated in terms of precision, accuracy and recoveries. Limits of detection and limits of quantitationwere in the range of 0.02-0.1 and 0.1-0.5 mg/mL, respectively. Whiskey cream beverages, fortified with commercial drugs at 20 mg/mL, were extracted and analyzed demonstrating the applicability of the method in forensic analysis.

An LC-MS method for the analysis of personal care and household products without sample preparation is presented. The method takes advantage of the Direct-electron ionization (EI) LC-MS interface for the quantitation of principal components, as well as for the identification of unknown or undeclared ingredients. The technique has proven its inertness toward matrix effects and the electron ionization allows quantitation and library identification. Commercially available products (shower gel, perfume, and hand cream) were diluted with methanol and injected directly into a nano-LC column. Limonene, linalool, and citral were selected as target compounds because of their use as fragrances in toiletry and detergent products. These and all other fragrances are commonly determined with GC-MS analysis, prior to sample cleanup, a procedure that can lead to analytes loss. The selected compounds are not detected with ESI because of their poor or very low response. Figures of merit and validation studies were executed and special attention was devoted to matrix-effects evaluation, because a sample preparation procedure is not involved. No matrix effects were observed, and the repeatability was excellent even after several weeks of operation. Products composition was investigated in full scan mode to determine the presence of unknown or not listed ingredients.

Endocrine disrupting compounds (EDCs) include organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), carbamate pesticides, and plasticizers, such as bisphenol A (BPA). They persist in the environment because of their degradation resistance and bioaccumulate in the body tissues of humans and other mammals. Many studies are focused on the possible correlation between in utero exposure to EDCs and adverse health hazards in fetuses and newborns. In the last decade, environmental pollution has been considered a possible trigger for Sudden Infant Death Syndrome (SIDS) and Sudden Intrauterine Unexplained Death Syndrome (SIUDS), the most important death-causing syndromes in fetuses and newborns in developed countries. In this work, a rapid and sensitive analytical method was developed to determine the level of OCPs and OPPs, carbamates, and phenols in human fetal and newborn tissues (liver and brain) and to unveil the possible presence of non-targeted compounds. The target analytes where selected on the basis of their documented presence in the Trentino-Alto Adige region, an intensive agricultural area in northern Italy. A liquid-solid extraction procedure was applied on human and animal tissues and the extracts, after a solid phase extraction (SPE) clean-up procedure, were analyzed by gas chromatography coupled to a quadrupole mass spectrometric detector (GC-qMS). A GC-TOFMS (time-of-flight) instrument, because of its higher full-scan sensitivity, was used for a parallel detection of non-targeted compounds. Method validation included accuracy, precision, detection, and quantification limits (LODs; LOQs), and linearity response using swine liver and lamb brain spiked at different concentrations in the range of 0.4-8000.0 ng/g. The method gave good repeatability and extraction efficiency.Method LOQs ranged from0.4-4.0 ng/g in the selectedmatrices. Good linearity was obtained over four orders of magnitude starting from LOQs. Isotopically labeled internal standar

One of the crucial tasks of pharmaceutical industry is to quantify the potential genotoxic impurities (PGIs) coming from the process of drug production. The European Medicines Agency (EMEA) imposes analytical testing limits in the order of g/g, depending on drug dosage and exposure period, that means the need of a sensitive and selective method of analysis. Liquid chromatography coupled to electrospray ionization mass spectrometry (LC–ESI-MS) has been demonstrated as the most versatile approach to detect PGIs in complex matrices. However, time consuming derivatization processes are needed to enhance sensitivity and selectivity, and to overcome matrix effects (ME) that may arise from active pharmaceutical ingredients (APIs) or excipients. We propose the use of the Direct-EI LC–MS as an alternative approach to detect and quantify PGIs in drug formulations. The Direct-EI LC–MS interface is based on electron ionization (EI) which is well suited for the detection of low molecular weight compounds of different polarity, without derivatization and with no sign of ME. The method has been successfully applied to the detection of PGIs belonging to the class of alkylation agents. Calibration experiments show satisfactory linearity and precision data. Recoveries in low enriched samples spanned from 55 to 82%, and were not affected by ME. The method limits of detection (LODs), varying from 0.13 to 1.5 g/g, were satisfactory for the quantitation of the target PGIs at the level required by regulatory agencies.

Introduction Pyrethrum extract is a mixture of six insecticidal compounds from the flower heads of Chrysanthemum cinerariaefolium L. Since they only have low to moderate mammalian toxicity they can be used as natural insecticides in agriculture or to develop low cost and safe dermatological formulations. Because of the thermal instability of pyrethrins, analytical methods based on liquid chromatography (LC) are preferred over those based on gas chromatography (GC). A few applications using LC with mass spectrometry detection are presented in the literature. Current protocols for their characterisation by LC rely on the use of less sophisticated detectors such as UV detection. Objective To develop the first liquid chromatography-electron ionisation-mass spectrometry (LC-EI-MS) method for pyrethrins detection and quantitation in pyrethrum extracts. Methodology A commercial pyrethrum extract and various samples of flower heads from C. cinerariaefolium L. were investigated using reversed-phase nano-liquid chromatography coupled to direct electron ionisation-mass spectrometry (nanoLC-direct EI-MS). The eluted compounds were identified through searches of the US National Institute of Standards and Technology (NIST) library, exploiting the direct EI capability to produce high quality EI mass spectra. Results The method demonstrated satisfactory sensitivity (limit of detection (LOD) range: 0.04-0.38 mg/g), linearity (R 2 range: 0.9740-0.9983) and precision (RSD% range: 4-13%) for the quantitation of the natural pyrethrins in extracts from C. cinerariaefolium L. Conclusion The nanoLC-direct EI-MS technique can be a useful tool for the detection of pyrethrins.

The purpose of this article is to underline the possibility of efficiently using electron ionization (EI) in liquid chromatography (LC) and mass spectrometry (MS). From a historical perspective, EI accompanied the first attempts in LC-MS but, owing to several technical shortcomings, it was soon outshined by soft, atmospheric pressure ionization (API) techniques. Nowadays, two modern approaches, supersonic molecular beam LC-MS and direct-EI LC-MS, offer a valid alterative to API, and preserve the advantages of EI also in LC-MS applications. These advantages can be summarized in three crucial aspects: automated library identification; identification of unknown compounds, owing to EI extensive fragment information; inertness to coeluted matrix interferences owing to very unlikely ion-ion and ion-molecule interactions in the EI gas-phase environment. The direct-EI LC-MS interface is a simple and efficient solution able to produce high-quality, interpretable EI spectra from a wide range of low molecular weight molecules of different polarity. Because of the low operative flow rates, this interface relies on a nano-LC technology that helps in reducing the impact of the mobile phase on the gas-phase environment of EI. This review provides an extensive discussion on the role of EI in LC-MS interfacing, and presents in detail several performance aspects of the direct-EI LC-MS interface, especially in terms of response, massspectral quality, and matrix effects. In addition, several key applications are also reported.

This review article will give an up-to-date and exhaustive overview on the efficient use of electron ionization (EI) to couple liquid chromatography and mass spectrometry (LC- MS) with an innovative interface called Direct-EI. EI is based on the gas-phase ionization of the analytes, and it is suitable for many applications in a wide range of LC-amenable compounds. In addition, thanks to its operating principles, it prevents unwelcome matrix effects (ME). In fact, although atmospheric pressure ionization (API) methodologies have boosted the use of LC-MS, the related analytical methods are sometime affected by inaccurate quantitative results, due to unavoidable and unpredictable ME. In addition, API's soft ionization spectra always demand for costly and complex tandem mass spectrometry (MS/MS) instruments, which are essential to acquire an "information-rich" spectrum and to obtain accurate quantitative information. In EI a one-stage analyzer is sufficient for a qualitative investigation and MS/MS detection is only used to improve sensitivity and to cut chemical noise. The technology illustrated here provides a robust and straightforward access to classical, well-characterized EI data for a variety of LC applications, and readily interpretable spectra for a wide range of areas of research. The Direct-EI interface can represent the basis for a forthcoming universal LC-MS detector for small molecules.

Produced formation waters (PFWs) represent the largest aqueous wastes that are normally discharged into the marine environment during the offshore gas production processes. The chemical additive diethylene glycol (DEG) is widely used in the gas production line and therefore can be found in the PFW, becoming of environmental concern. In this study, a new method has been developed for trace determination of DEG in sea water samples collected around offshore gas platforms. The method is based on liquid chromatography coupled to electrospray ionization mass spectrometry (LC-ESI-MS). Prior to analysis, water samples were derivatized using the Schotten-Baumann method for the benzoylation of glycols. The derivatization procedure allowed us to maximize the ESI-MS response of DEG and minimize the influence of interfering compounds. The method was validated and allowed a quantification of DEG in sea water samples with a method LOD of 0.4 ng/mL. The applicability of the procedure was demonstrated by analyzing sea water samples collected around eight gas platforms located in the Adriatic Sea (Italy).

A major limitation in quantitative analysis with electrospray ionization mass spectrometry (ESI-MS) is represented by the so-called matrix effects in which the matrix coextracted with the analytes can alter the signal response, causing either suppression or enhancement, resulting in poor analytical accuracy, linearity, and reproducibility. In the direct electron ionization liquid chromatography-mass spectrometry (direct-EI LC-MS) interface the ionization process is based on electron impact ionization, and it occurs in the gas phase and is not influenced by coeluted matrix compounds. In this work we quantitatively evaluated matrix effects on enriched environmental and biological samples, with different extraction procedures, using ESI and direct-EI LC-MS. As expected, the samples analyzed with direct-EI were not affected by matrix composition, whereas with ESI we observed either signal suppression or enhancement, depending on the sample nature.